diff --git a/dispatch.go b/dispatch.go
index 87fe01b..5f17695 100644
--- a/dispatch.go
+++ b/dispatch.go
@@ -45,6 +45,7 @@ func (d *dispatcher) handleRequest(payload []byte) []byte {
 		Query      map[string]string `json:"query"`
 		ProjectID  string            `json:"project_id"`
 		CallerID   string            `json:"caller_id"`
+		UserID     string            `json:"user_id"`
 		CallerRole string            `json:"caller_role"`
 		Headers    map[string]string `json:"headers"`
 		Body       []byte            `json:"body"`
@@ -70,6 +71,7 @@ func (d *dispatcher) handleRequest(payload []byte) []byte {
 		Body:       hr.Body,
 		Caller: CallerIdentity{
 			CallerID:   hr.CallerID,
+			UserID:     hr.UserID,
 			CallerRole: hr.CallerRole,
 			ProjectID:  hr.ProjectID,
 		},
diff --git a/native_backends.go b/native_backends.go
index 347d069..16a0bf3 100644
--- a/native_backends.go
+++ b/native_backends.go
@@ -45,6 +45,9 @@ func (b *stubConfigBackend) Get(_ string) (string, bool) { return "", false }
 // EmitEvent is a no-op outside WASM.
 func EmitEvent(_ string, _ any) {}
 
+// RecordActivity is a no-op outside WASM.
+func RecordActivity(_, _, _, _ string, _ any) {}
+
 // ptrOf and hostError are used by wasm_backends.go (wasip1 only); provide
 // stubs here so the non-WASM build does not need them.
 //nolint:unused // used in wasm_backends.go in WASM builds
diff --git a/request.go b/request.go
index b8a982e..da03e3b 100644
--- a/request.go
+++ b/request.go
@@ -7,6 +7,9 @@ import "encoding/json"
 type CallerIdentity struct {
 	// CallerID is the project_member UUID of the caller.
 	CallerID string `json:"caller_id"`
+	// UserID is the authenticated user's UUID (JWT sub claim).
+	// Use this as actor_id when recording task activities.
+	UserID string `json:"user_id"`
 	// CallerRole is the role name of the caller within the project.
 	CallerRole string `json:"caller_role"`
 	// ProjectID is the project the request is scoped to.
diff --git a/wasm_backends.go b/wasm_backends.go
index 9d77624..8e6e2eb 100644
--- a/wasm_backends.go
+++ b/wasm_backends.go
@@ -179,6 +179,38 @@ func EmitEvent(topic string, payload any) {
 	)
 }
 
+// ── RecordActivity ────────────────────────────────────────────────────────────
+
+// activityInput is the JSON shape sent to the paca.activity_record host function.
+type activityInput struct {
+	TaskID       string `json:"task_id"`
+	ProjectID    string `json:"project_id"`
+	ActorID      string `json:"actor_id"`
+	ActivityType string `json:"activity_type"`
+	Content      any    `json:"content"`
+}
+
+// RecordActivity appends a task-activity event to the paca activity stream so
+// that it is persisted to PostgreSQL by the ActivityConsumer worker.
+// actorUserID should be req.Caller.UserID (the authenticated user's UUID).
+// content must be JSON-encodable and match the expected shape for activityType.
+func RecordActivity(taskID, projectID, actorUserID, activityType string, content any) {
+	inp := activityInput{
+		TaskID:       taskID,
+		ProjectID:    projectID,
+		ActorID:      actorUserID,
+		ActivityType: activityType,
+		Content:      content,
+	}
+	payloadBytes, err := json.Marshal(inp)
+	if err != nil {
+		return
+	}
+	if !hostActivityRecord(int64(ptrOf(payloadBytes)), int64(len(payloadBytes))) {
+		return
+	}
+}
+
 // ── Helpers ───────────────────────────────────────────────────────────────────
 
 //go:nocheckptr
diff --git a/wasm_imports.go b/wasm_imports.go
index 3cb4243..8393a94 100644
--- a/wasm_imports.go
+++ b/wasm_imports.go
@@ -49,6 +49,12 @@ func hostStorageDelete(keyPtr, keyLen int64) int32
 //go:noescape
 func hostEventEmit(topicPtr, topicLen, payloadPtr, payloadLen int64) int32
 
+// paca.activity_record(payloadPtr i64, payloadLen i64) -> ok i32
+//
+//go:wasmimport paca activity_record
+//go:noescape
+func hostActivityRecord(payloadPtr, payloadLen int64) int32
+
 // paca.config_get(keyPtr i64, keyLen i64, valuePtrPtr i64, valueLenPtr i64)
 //
 //go:wasmimport paca config_get